Need advice on buying dart swinger

I have been looking for a 99+ mustang for acouple of months than yesterday my buddy told me about a 75 dodge dart swinger his friend is selling. So i went and checked it out and i instantly wanted it but before i buy it i thought i should do some research. It originally came from arizona and is rust free. It was a 6cyl and the guy replaced it with a 360. It was just recently painted orange and the body looks to be in perfect condition. The only thing is the interior needs to be redone in my opinion(seats and doorpanels) and the windsheild needs to be resealed because it leaks in one corner. Other than the body the car needs alittle work. It is an automatic and it runs good. The guy is asking 6000 for the car as is. Does this sound like an ok deal. I dont know much about old muscle cars but i really like this one. Any advice is very appreciated. THANKS